Paper No. 90-3
Presentation Time: 9:00 AM-5:30 PM
DETRITAL ZIRCON SIGNATURE OF THE MESOPROTEROZOIC SMITH SOUND GROUP AND CAMBRIAN DALLAS BUGT FORMATION, ARCTIC PLATFORM, EAST CENTRAL ELLESMERE ISLAND
The Franklinian basin, northern Canada and Greenland, marks the northern passive margin of Laurentia formed after breakup of Rodinia. Ediacaran-Cambrian clastic strata on Ellesmere Island preserve the transition from shallow-water to deep-water, shelf to slope depositional environments. Detrital zircon analyses define a prominent 1000-1400 Ma population in deep-water strata of the Hazen fold belt (Beranek et al., 2013; Can. J. Earth Sci.), but this population is generally lacking in the shallow-water shelf strata of the Central Ellesmere fold belt (Anfinson et al., 2012; GSA Bulletin). U/Pb analyses of detrital zircon from clastic rocks of the Mesoproterozoic Smith Sound Group and Early Cambrian Dallas Bugt Formation exposed on the Arctic platform on east central Ellesmere Island further evaluate this variation in provenance signature across the passive margin. Sandstone from the Smith Sound Group exposed on Bache Peninsula is dominated by a 1800-2050 Ma population with subpeaks at 1900 and 1975 Ma. Minor populations occur at 1370-1565 and 2300-2800 Ma and minor peaks appear at 2515 and 2705 Ma. A sandstone sample from the overlying Dallas Bugt Formation lacks the younger population but contains similar 1800-2050 and 2300-2800 Ma populations with major peaks at 1835, 2545 and 2705 Ma. Dallas Bugt sandstone resting nonconformably on Paleoproterozoic granulite-facies metamorphic basement in Jokel Fiord has a bimodal population with major peaks at 1930 and 2510 Ma; minor peaks lie at 1960 and 2450 Ma. Dallas Bugt sandstone collected above the Paris Glacier thrust at the head of Franklin Pierce Bay gave major peaks at 1835 and 2695 Ma with minor peaks at 2455, 2595, 2820 Ma. Collectively, the Cambrian samples lack 1000-1400 Ma “Grenville”-age detritus but display peaks from ca. 1750-1950, 2350-2550, 2650-2800 Ma that are broadly similar to both shallow- and deep-water samples in the Franklinian basin. The zircon populations are interpreted to record sourcing from local basement exposures including recycling from the Smith Sound Group. The prominent peaks at ca. 2500 Ma are not characteristic of the Franklinian basin detrital zircon record but may record extension of the Queen Maud block and parallel Thelon tectonic zone from central Nunavut to eastern Ellesmere Island.